Described below is a storage structure for a solid electrolyte battery.
Solid electrolyte batteries are based on the operating principle of solid electrolyte fuel cells, which are extended by additional provision of at least one storage element to give a solid electrolyte battery.
Known solid electrolyte fuel cells of the generic type, for example oxide-ceramic fuel cells, also referred to in the specialist field as SOFC (solid oxide fuel cells), are known from international published specification WO 2011/019455 A1, in which the concept of SOFC-derived solid electrolyte batteries is addressed in detail. Solid electrolyte batteries of this kind work with an operating temperature above 500° C., at which the solid electrolyte has sufficient ion conductivity for oxygen ions.
A storage medium intended for operation of a rechargeable solid electrolyte battery typically includes particles suitable for formation of a redox pair as a constituent of at least one storage element of the solid electrolyte battery. The particles are typically formed of metal and/or metal oxide. According to the battery state (charging or discharging), this storage medium is reduced or oxidized. The storage structure typically has a gas-permeable porous microstructure, i.e. a skeleton-like structure of the storage medium with high open porosity.
In a multitude of cyclical charging and discharging operations, i.e. reduction and oxidation operations, of the storage medium, the storage medium at the high operating temperatures applied has a tendency to coarsening and/or sintering of the particles of the active storage medium. This leads to a continuous change in the storage structure and especially to a decrease in the surface area of the storage medium, which is reflected in increasingly poorer charging and discharging characteristics and in a decrease in the useful capacity.
There have therefore already been proposals of storage structures using storage media based on oxide dispersion-strengthened particles (ODS) particles. Such a storage structure features more prolonged stability, which corresponds to a higher achievable number of cycles of charging and discharging operations without any significant losses in useful capacity. Additionally known is use of a ceramic matrix which forms an intergranular (i.e. between the particles of the storage medium) support skeleton to space apart the particles of the storage medium.
Both dispersion strengthening of the particles of the storage medium and a coarse-grained ceramic matrix slow down coarsening of the particles of the storage medium, but cannot reverse it. More particularly, it is not possible at present to regenerate an aged storage structure to the effect that particle coarsening of the storage medium is reversed.